Implantable flexible circuit leads and methods of use

ABSTRACT

Devices, systems and methods are provided for stimulation of tissues and structures within a body of a patient. In particular, implantable leads are provided which are comprised of a flexible circuit. Typically, the flexible circuit includes an array of conductors bonded to a thin dielectric film. Example dielectric films include polyimide, polyvinylidene fluoride (PVDF) or other biocompatible materials to name a few. Such leads are particularly suitable for stimulation of the spinal anatomy, more particularly suitable for stimulation of specific nerve anatomies, such as the dorsal root (optionally including the dorsal root ganglion).

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/952,062, filed Dec. 6, 2007, which claims priority of U.S.Provisional Patent Application No. 60/873,459, filed Dec. 6, 2006 (Atty.Docket No. 10088-702.101); and U.S. Provisional Patent Application No.60/873,496, filed Dec. 6, 2006 (Atty. Docket No. 10088-704.101), both ofwhich are incorporated herein by reference for all purposes.

BACKGROUND

The application of specific electrical energy to the spinal cord for thepurpose of managing pain has been actively practiced since the 1960s. Itis known that application of an electrical field to spinal nervoustissue can effectively mask certain types of pain transmitted fromregions of the body associated with the stimulated nervous tissue. Suchmasking is known as paresthesia, a subjective sensation of numbness ortingling in the afflicted bodily regions. Application of electricalenergy has been based on the gate control theory of pain. Published in1965 by Melzack and Wall, this theory states that reception of largenerve fiber information, such as touch, sense of cold, or vibration,would turn off or close the gate to reception of painful small nervefiber information. The expected end result would, therefore, be painrelief. Based on the gate control theory, electrical stimulation oflarge fibers of the spinal cord cause small fiber information to bereduced or eliminated at that spinal segment and all other informationdownstream from that segment would be reduced or eliminated as well.Such electrical stimulation of the spinal cord, once known as dorsalcolumn stimulation, is now referred to as spinal cord stimulation orSCS.

FIGS. 1A-1B illustrate conventional placement of an SCS system 10.Conventional SCS systems include an implantable power source orimplantable pulse generator (IPG) 12 and an implantable lead 14. SuchIPGs 12 are similar in size and weight to pacemakers and are typicallyimplanted in the buttocks of a patient P. Using fluoroscopy, the lead 14is implanted into the epidural space E of the spinal column andpositioned against the dura layer D of the spinal cord S, as illustratedin FIG. 1B. The lead 14 is implanted either through the skin via anepidural needle (for percutaneous leads) or directly and surgicallythrough a mini laminotomy operation (for paddle leads).

FIG. 2 illustrates example conventional paddle leads 16 and percutaneousleads 18. Paddle leads 16 typically have the form of a slab of siliconrubber having one or more electrodes 20 on its surface. Exampledimensions of a paddle lead 16 is illustrated in FIG. 3. Percutaneousleads 18 typically have the form of a tube or rod having one or moreelectrodes 20 extending therearound. Example dimensions of apercutaneous lead 18 is illustrated in FIG. 4.

Implantation of a percutaneous lead 18 typically involves an incisionover the low back area (for control of back and leg pain) or over theupper back and neck area (for pain in the arms). An epidural needle isplaced through the incision into the epidural space and the lead isadvanced and steered over the spinal cord until it reaches the area ofthe spinal cord that, when electrically stimulated, produces acomfortable tingling sensation (paresthesia) that covers the patient'spainful area. To locate this area, the lead is moved and turned on andoff while the patient provides feedback about stimulation coverage.Because the patient participates in this operation and directs theoperator to the correct area of the spinal cord, the procedure isperformed with local anesthesia.

Implantation of paddle leads 16 typically involves performing a minilaminotomy to implant the lead. An incision is made either slightlybelow or above the spinal cord segment to be stimulated. The epiduralspace is entered directly through the hole in the bone and a paddle lead16 is placed over the area to stimulate the spinal cord. The target areafor stimulation usually has been located before this procedure during aspinal cord stimulation trial with percutaneous leads 18.

Although such SCS systems have effectively relieved pain in somepatients, these systems have a number of drawbacks. To begin, asillustrated in FIG. 5, the lead 14 is positioned upon the spinal corddura layer D so that the electrodes 20 stimulate a wide portion of thespinal cord and associated spinal nervous tissue. The spinal cord is acontinuous body and three spinal levels of the spinal cord areillustrated. For purposes of illustration, spinal levels aresub-sections of the spinal cord S depicting that portion where thedorsal root DR and ventral root VR join the spinal cord S. Theperipheral nerve N divides into the dorsal root DR and the dorsal rootganglion DRG and the ventral nerve root VR each of which feed into thespinal cord S. An ascending pathway 17 is illustrated between level 2and level 1 and a descending pathway 19 is illustrated from level 2 tolevel 3. Spinal levels can correspond to the vertebral levels of thespine commonly used to describe the vertebral bodies of the spine. Forsimplicity, each level illustrates the nerves of only one side and anormal anatomical configuration would have similar nerves illustrated inthe side of the spinal cord directly adjacent the lead.

Motor spinal nervous tissue, or nervous tissue from ventral nerve roots,transmits muscle/motor control signals. Sensory spinal nervous tissue,or nervous tissue from dorsal nerve roots, transmits pain signals.Corresponding dorsal and ventral nerve roots depart the spinal cord“separately”; however, immediately thereafter, the nervous tissue of thedorsal and ventral nerve roots are mixed, or intertwined. Accordingly,electrical stimulation by the lead 14 often causes undesirablestimulation of the motor nerves in addition to the sensory spinalnervous tissue.

Because the electrodes span several levels the generated stimulationenergy 15 stimulates or is applied to more than one type of nerve tissueon more than one level. Moreover, these and other conventional,non-specific stimulation systems also apply stimulation energy to thespinal cord and to other neural tissue beyond the intended stimulationtargets. As used herein, non-specific stimulation refers to the factthat the stimulation energy is provided to all spinal levels includingthe nerves and the spinal cord generally and indiscriminately. Even ifthe epidural electrode is reduced in size to simply stimulate only onelevel, that electrode will apply stimulation energy Indiscriminately toeverything (i.e. all nerve fibers and other tissues) within the range ofthe applied energy. Moreover, larger epidural electrode arrays may aftercerebral spinal fluid flow thus further altering local neuralexcitability states.

Another challenge confronting conventional neurostimulation systems isthat since epidural electrodes must apply energy across a wide varietyof tissues and fluids (i.e. CSF fluid amount varies along the spine asdoes pia mater thickness) the amount of stimulation energy needed toprovide the desired amount of neurostimulation is difficult to preciselycontrol. As such, increasing amounts of energy may be required to ensuresufficient stimulation energy reaches the desired stimulation area.However, as applied stimulation energy increases so too increases thelikelihood of deleterious damage or stimulation of surrounding tissue,structures or neural pathways.

Improved stimulation devices, systems and methods are desired thatenable more precise and effective delivery of stimulation energy. Suchdevices should be reliably manufactural, appropriately sized, costeffective and easy to use. At these some of these objectives will befulfilled by the present invention.

SUMMARY

The present invention provides devices, systems and methods forstimulation of tissues and structures within a body of a patient. Inparticular, implantable leads are provided which are flexible, reliableand easily manufacturable for a variety of medical applications. Suchleads are particularly suitable for stimulation of the spinal anatomy,more particularly suitable for stimulation of specific nerve anatomies,such as the dorsal root (optionally including the dorsal root ganglion).Such specificity is enhanced by the design attributes of the leads.

The implantable leads of the present invention utilize a flexiblecircuit. Typically, the flexible circuit includes an array of conductorsbonded to a thin dielectric film. Example dielectric films includepolyimide, polyvinylidene fluoride (PVDF) or other biocompatiblematerials to name a few. The conductors are comprised of biocompatibleconductive metal(s) and/or alloy(s), such as gold, titanium, tungsten,titanium tungsten, titanium nitride, platinum, iridium, orplatinum-iridium alloy, which is plated onto the dielectric film. Thebase and metal construct is then etched to form a circuit (i.e. anelectrode pad contact and a “trace” to connect the pad to a connector).In some embodiments, redundancy in the “traces” is provided by utilizingmultiple traces to the same contact to improve reliability.

Some advantages of leads comprised of a flexible circuit overtraditional leads are greater reliability, size and weight reduction,elimination of mechanical connectors, elimination of wiring errors,increased impedance control and signal quality, circuit simplification,greater operating temperature range, and higher circuit density. Inaddition, lower cost is another advantage of using flexible circuits. Insome embodiments, the entire lead will be formed from a flexiblecircuit. Also, in some embodiments, the lead will include an integratedconnector for connection to an electronics package.

One main advantage of the flexible circuitry lead is its thinness andtherefore flexibility. The thickness of the dielectric film typicallyranges from 7.5 to 125 μm (0.3 to 5 mils). However, in some embodiments,the lead will be comprised of a flexible circuit having a base layer of0.5 to 2 mils thick.

The flexible circuitry used in the present invention may besingle-sided, double-sided, or multilayer. Single-sided circuits arecomprised of a single conductive layer and are the simplest type offlexible circuit. In some instances, a technique known as back baring ordouble access may be used to create a special type of single layercircuit. This technique allows access to the metal conductors from bothsides of the circuit and is used when component soldering or otherinterconnection is desired on two sides of the circuit.

Double-sided circuits, as the name implies, are circuits with twoconductive layers that are usually accessible from both sides.Multilayer refers to two or more layers which have been stacked andbonded.

In some embodiments, the flexible circuit is created with methods of thepresent invention. For example, metal deposition, such as vapordeposition, sputtering techniques or plasma fields, is used to coat thefilm structure with metal to form the electrodes and traces. In suchembodiments, the film structure is comprised of polyvinylidene fluoride(PVDF). The process may utilize PVDF in either sheet form or,preferably, in roll form, with cooling to reduce thermal stressesbetween the dielectric film structure and the metal coat. The PVDF iscoated with an adhesion layer, such as titanium or titanium-tungstenalloy, which will improve the reliability of the bond between thedielectric film structure and the electrodes and traces that will bedeposited thereon. The adhesion layer is then coated, such as sputtercoated, with a seed layer of conductive biocompatible metal, such asgold or platinum. After such metallization, the seed layer is patterned,either by photolithography and wet etch, or by laser ablation to formthe shapes of the traces and electrodes. After patterning the seed layerof metal, sputtering or electroplating is used to increase the thicknessof the traces in order to improve conductivity, and then again to createthe final electrode working surface. Possible trace materials includeplatinum, gold, iridium-oxide, a combination thereof or any otherconductive biocompatible metal suitable for implantation. The electrodesurface may be coated over the entire metallization of the lead, orselectively and only over the intended electrode surface with an inertmetal such as platinum, iridium-oxide, or combination thereof. In someembodiments, the adhesion layer of titanium or titanium-tungsten alloyis sputter coated with a seed layer of gold, then sputter coated withplatinum and then electroplated with platinum. In other embodiments, theadhesion layer of titanium or titanium-tungsten alloy is sputter coatedwith a seed layer of gold, then electroplated with gold and thenelectroplated with platinum. In yet other embodiments, the adhesionlayer of titanium or titanium-tungsten alloy is sputter coated with aseed layer of platinum, then electroplated with platinum. It may beappreciated that other combinations may also be used.

In a first aspect of the present invention, a method is provided forstimulating a tissue within a body. In some embodiments, the methodcomprises positioning a lead comprising a flexible circuit having atleast one electrode so that at least one of the at least one electrodeis disposed near a dorsal root. Optionally, the positioning ensures thatat least one of the at least one electrode is disposed near a dorsalroot ganglion of the dorsal root. The method also includes supplyingelectrical energy to the at least one of the at least one electrode soas to stimulate at least a portion of the dorsal root. In someembodiments, the portion of the dorsal root comprises a dorsal rootganglion.

Optionally, the method may include advancing the lead through a foramenand/or advancing the lead through an epidural space. Typically, themethod further comprises joining the lead with an implantable pulsegenerator. In such instances, the method typically includes implantingthe lead and the implantable pulse generator wholly within the body.

In a second aspect of the present invention, a flexible circuit lead isprovided for stimulating a body tissue. In some embodiments, the leadcomprises an elongate structure having a distal end configured to bepositioned near a dorsal root and a proximal end coupleable with a pulsegenerator, wherein the structure comprises a dielectric film. The leadalso includes at least one electrode disposed near the distal end and atleast one conductive trace extending from the at least one electrodetoward the proximal end so that stimulation energy is transmittable fromthe coupled pulse generator to the at least one electrode so as tostimulate the at least a portion of the dorsal root.

In some embodiments, the at least one electrode is comprised of abiocompatible conductive metal, alloy or combination of these platedonto the dielectric film. In such instances, the biocompatibleconductive metal, alloy or combination may include gold, titanium,tungsten, titanium tungsten, titanium nitride, platinum, iridium orplatinum-iridium alloy. Often, the dielectric film has a thickness inthe range of approximately 7.5 to 125 μm.

In some embodiments, the at least one electrode comprises a plurality ofelectrodes arranged substantially linearly along a longitudinal axis ofthe distal end. In other embodiments, the at least one electrodecomprises a plurality of electrodes arranged substantially linearlyalong a horizontal axis of the distal end. Optionally, the at least oneelectrode comprises a plurality of electrodes arranged in asubstantially circular or arc shape.

In some instances, the distal end has a pronged shape including at leasttwo prongs. In such instances, one of the at least one electrodes may bedisposed near a tip of one of the at least two prongs. In someembodiments, the distal end is configured to wrap around the bodytissue. And typically, the distal end of the elongate structure ispassable through a needle.

In a third aspect of the present invention, a lead is provided forstimulating a body tissue comprising: an elongate structure having aproximal end coupleable with a pulse generator and a distal end havingtwo edges which are capable of being positioned in opposition, whereinthe distal end includes at least two electrodes which generally opposeeach other when the edges are positioned in opposition so as tostimulate the body tissue. Typically the body tissue comprises a dorsalroot ganglion.

In some embodiments, the distal end forms a V-shape or U-shape when thetwo edges are positioned in opposition which allows the body tissue tobe positioned at least partially within the V-shape or U-shape. Thedistal end may comprise two elongate elements, each element having oneof the two edges. In such instances, the two elongate elements may bepositionable in linear alignment with a longitudinal axis of theelongate structure.

In some embodiments, the distal end has a rounded shape wherein sides ofthe rounded shape form the two edges. In such embodiments, the sides ofthe rounded shape may curl or fold towards each other to position thetwo edges in opposition.

Typically, the elongate structure comprises a dielectric film. Thedielectric film may have a thickness in the range of approximately 7 to125 μm. Also, the at least two electrodes may be comprised of abiocompatible conductive metal, alloy or combination of these plated onthe dielectric film. Typically, the distal end is passable through aneedle.

In another aspect of the present invention, a system for stimulating abody tissue is provided comprising: a first elongate structure havingfirst proximal end coupleable with a pulse generator and a first distalend, wherein the first distal end has a first inner surface having afirst electrode disposed thereon, and a second elongate structure havinga second proximal end coupleable with the pulse generator and a seconddistal end, wherein the second distal end has a second inner surfacehaving a second electrode disposed thereon. The first and secondelongate structures are joined so that the first and second electrodesare capable of directing stimulation energy toward each other, andwherein the first and second distal ends are moveable away from eachother so as to allow the body tissue to be positioned at least partiallytherebetween to receive the stimulation energy.

In some embodiments, the first and second elongate structures areslidably joined. Optionally, the first distal end is movable by recoilforce. In some systems, the first distal end is attachable to a firstobturator which is capable of moving the first distal end. In thesesystems, the first obturator may be configured to dissect tissue whileit moves the first distal end. Optionally, the first obturator may beadvanceable from a delivery device so as to advance the first distal endand move the first distal end away from the second distal end.

Typically, the first elongate structure comprises a dielectric film.And, typically, the body tissue comprises a dorsal root ganglion.Optionally, the distal end may be passable through a needle.

In some embodiments, the first elongate structure includes a firstcontact pad disposed on an outer surface of the proximal end of thefirst elongate structure, wherein the first contact pad provideselectrical connection from the first electrode to the pulse generator.And in some embodiments, the second elongate structure includes a secondcontact pad disposed on an outer surface of the proximal end of thesecond elongate structure, wherein the second contact pad provideselectrical connection from the second electrode to the pulse generator.

In another aspect of the present invention, a flexible circuit lead isprovided for stimulating a body tissue, wherein the lead comprises anelongate structure having a distal end comprising at least one electrodeon a dielectric film, and wherein the distal end is movable to at leastpartially surround the body tissue and direct stimulation energy fromthe at least one electrode toward the body tissue. Typically, the distalend is passable through a needle.

In some embodiments, the distal end is moveable by curling or uncurlingso as to at least partially surround the body tissue. In otherembodiments, the distal end is moveable by folding or unfolding so as toat least partially surround the body tissue.

Typically, the distal end comprises opposing elements which move towardor away from each other so as to at least partially surround the bodytissue. In some instances, the opposing elements may move independently.Optionally, the opposing elements may form a V-shape.

In another aspect of the present invention, a device is provided forstimulating a body tissue, wherein the device comprises an elongateshaft having an outer surface and a lead having a at least oneelectrode, wherein the lead is mounted on the outer surface of theelongate shaft so that the at least one electrode is positionable near adorsal root for stimulation. Typically, the lead is comprised of anelongate structure comprising a dielectric film. In such instances, theat least one electrode may be comprised of a biocompatible conductivemetal, alloy or combination of these plated onto the dielectric film.

In some embodiments, the elongate shaft includes a lumen therethroughconfigured for passage of a stylet. In some embodiments, the at leastone electrode comprises a plurality of electrodes positioned so as towrap at least partially around the elongate shaft. And in someembodiments, the elongate shaft is configured for implantation in anarrangement so that the at least one electrode is positioned near adorsal root ganglion.

In yet another aspect of the present invention, a lead is provided forstimulating a body tissue, wherein the lead comprises a first elongatestructure having a first distal end configured to be positioned near thebody tissue and a first proximal end coupleable with a pulse generator.The first elongate structure has a first electrode disposed near thefirst distal end. The lead also includes a second elongate structurehaving a second distal end, a second proximal end and a second electrodedisposed near the second distal end. The second elongate structure isattached to the first elongate structure in a layered configuration sothat stimulation energy is transmittable from the coupled pulsegenerator to the first and second electrode so as to stimulate the bodytissue.

In some embodiments, the layered configuration offsets the distal ends.In some embodiments, the first and second electrodes are arrangedsubstantially linearly along a longitudinal axis of the distal end.

In some instances, the lead further comprises a third elongate structurehaving a third proximal end, a third distal end and a third electrodedisposed near the third distal end, wherein the third elongate structureis attached to the second elongate structure in a layered configurationso that stimulation energy is transmittable from the coupled pulsegenerator to the third electrode so as to stimulate the body tissue.Typically, the distal ends of the layered configuration of elongatestructures are passable through a needle.

In some embodiments, the at least one conductive trace extends from eachelectrode toward its respective proximal end. In such embodiments, eachconductive trace may have a shape so that the layered configurationbalances the conductive traces. At least one of the at least oneconductive traces may have a zig-zag or serpentine shape.

Typically, the first elongate structure comprises a dielectric film. Insuch instances, the first electrode is comprised of a biocompatibleconductive metal, alloy or combination of these plated onto thedielectric film. Optionally, the biocompatible conductive metal, alloyor combination includes gold, titanium, tungsten, titanium tungsten,titanium nitride, platinum, iridium or platinum-iridium alloy.

Other objects and advantages of the present invention will becomeapparent from the detailed description to follow, together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1B, 2, 3, 4, 5 illustrate prior art.

FIG. 6, 6A, 6B illustrates an embodiment of a flexible circuit lead ofthe present invention.

FIGS. 7A, 7B, 7C, 7D illustrate a variety of approaches to an exampletarget anatomy for positioning the leads of the present invention.

FIG. 8 illustrates electrodes positioned more proximal to the distal tipof the lead.

FIG. 9 illustrates a distal end of an embodiment of a flexible circuitlead of the present invention.

FIG. 10 illustrates a proximal end of an embodiment of a flexiblecircuit lead of the present invention

FIGS. 11A-11B illustrate a layered lead comprising two or moreindividual leads which are layered and bonded together.

FIG. 12 illustrates an embodiment of a layered lead in an expanded view.

FIGS. 13, 13A, 13B illustrates an example of a lead which may be used inlayering.

FIG. 14 illustrates an example process and fixture for forming a layeredlead.

FIG. 15A illustrates a lead of the present invention having an oval,rounded or circular distal end.

FIG. 15B illustrates the lead of FIG. 15A positioned so that its distalend is in proximity to a dorsal root ganglion.

FIGS. 16A, 16B, 16C illustrate a distal end of a lead which is curlableor rollable.

FIG. 17 illustrates a lead of the present invention having a prongeddistal end.

FIG. 18 illustrates the lead of FIG. 17 positioned so that its distalend is in proximity to a dorsal root ganglion.

FIGS. 19-20 illustrate an embodiment of a shaped flexible circuit leadwhich can form a three dimensional shape.

FIG. 21A-21B illustrate a delivery device comprises a flattened tubehaving a distal end and a pair of obturators which are advanceable outof the distal end.

FIG. 22 illustrates a flexible circuit lead attached to a deliverydevice.

FIG. 23 illustrates a flexible circuit lead particularly suited forwrapping around a catheter.

FIGS. 24-25 illustrate an example connector of the present invention.

DETAILED DESCRIPTION

FIG. 6 illustrates an embodiment of a lead 100 of the present invention.The lead 100 is comprised of a flexible circuit. In particular, the lead100 is comprised of an elongate structure 107 having a distal end 102and a proximal end 104. The distal end 102 is configured to bepositioned near a target body tissue and the proximal end 104 iscoupleable with a power source or implantable pulse generator (IPG).FIG. 6A provides a detailed illustration of the distal end 102 of thelead 100 of FIG. 6. As shown, the lead 100 includes at least oneelectrode 106 plated on the dielectric film. In this embodiment, fourelectrodes 106 are present in an array. It may be appreciated that anynumber of electrodes 106 may be used in any desired arrangement,including longitudinally aligned individually (as shown) or in pairs orsets. FIG. 6B provides a detailed illustration of the proximal end 104of the lead 100 of FIG. 6. The proximal end 104 includes contact pads108 that are used to connect with the IPG. In this embodiment, fourcontact pads 108 are shown, one corresponding to each electrode 106.Each contact pad 108 is electrically connected with an electrode 106through a conductive trace 110 that extends therebetween, thus from theproximal end 104 to the distal end 102. Stimulation energy istransmitted from the IPG through the contact pads 108 and through trace110 to the electrodes 106 which stimulate the desired target tissue. Itmay be appreciated that in some embodiments, the conductive traces 110are arranged so that each contact pad 108 is connected with more thanone electrode 106 or each electrode 106 is connected with more than onecontact pad 108.

The leads 100 of the present invention may be used to stimulate avariety of target tissues, particularly a dorsal root ganglion DRG.FIGS. 7A-7D illustrate various approaches to the DRG and positioning alead 100 of the present invention so as to stimulate the DRG.Embodiments of these approaches include passing through, near or alongone or more posterior or lateral openings in the bony structure of thespinal column. An example of a posterior opening is an opening betweenadjacent spinous processes. An example of a lateral opening is theforamen or opening at least partially defined by the articulatingprocesses and the vertebrae. FIG. 7A illustrates a retrograde (100 a),antegrade (100 b) and lateral approach (100 c) to the dorsal root andDRG from the spinal column. FIG. 7B illustrates a retrograde (100 d),antegrade (100 e) and lateral approach (100 f) to the dorsal root andDRG from outside of the spinal column, such as from a side ortraditional percutaneous approach. FIG. 7C illustrates an antegradeapproach to a dorsal root and DRG between an articulating process (notshown) and the vertebral body (not shown). FIG. 7D illustrates aretrograde approach to a dorsal root and DRG between an articulatingprocess (not shown) and a vertebral body (not shown). The leads of thepresent invention may also be positioned by any other suitable method orapproach. One exemplary retrograde approach is a retrograde translaminarapproach. One exemplary approach is an antegrade translaminar approach.One exemplary lateral approach is a transforamenal approach.

As mentioned above, each lead 100 includes at least one electrode 106,preferably two, three, four, five, six or more electrodes. The lead 100is preferably aligned so that at least one of the at least oneelectrodes 160 is positioned as close to the target location aspossible, for example, on the DRG. In some situations, the DRG has asize of 5-10 mm. Thus, in some embodiments, a lead 100 having four 1 mmsquare electrodes spaced 1-2 mm apart would allow all four of theelectrodes to simultaneously contact the DRG. In such an instance, allfour electrodes may provide stimulation energy. In other embodiments,the electrodes may be sized or shaped so that less than the total numberof electrodes are desirably positioned on or near the target location.This may also occur due to placement of the lead. In such instances, asubset of the electrodes may provide stimulation energy, preferably oneor more electrodes positioned closest to the target location. Thisassists in reducing or eliminating undesired stimulation of non-targetanatomies.

It may be appreciated that the electrodes may be positioned at anylocation along the length of the lead, may have any suitable shape andany suitable spacing. FIG. 8 illustrates electrodes 160 positioned moreproximal to the distal tip of the lead 100. Thus, a portion of the lead100 having no electrodes 160 extends distally beyond the last electrode160. When the electrodes 160 are positioned over the target location,the distal most end of the lead 100 extends therefrom, such astransforamenally. Such extension may assist in anchoring the lead. Itmay be appreciated that the lead 100 of FIG. 8 may alternatively bepositioned by any of the approaches listed above, or any otherapproaches.

FIG. 9 illustrates a distal end 102 of another embodiment of a flexiblecircuit lead 100 of the present invention. In this embodiment, threeelectrodes 106 are disposed in an array on the film structure 107, eachelectrode 106 having a trace 110 which extends toward the proximal end104 of the lead. In this embodiment, the lead 100 also includes ananchoring feature 118 which assists in anchoring the lead 100 withintissue to resist migration of the lead 100. In this embodiment, theanchoring feature 118 comprises a plurality of serrations or notches 120cut into the film structure 107. The notches 120 may have any suitableshape, dimension or spacing. Likewise, the notches 120 may besymmetrical, non-symmetrical, present along one edge 111 of the filmstructure 107 or along more than one edge. In this embodiment, theanchoring feature 118 extends distally of the distal-most electrode 106,however it may disposed at any location along the lead 100.

FIG. 10 illustrates an example of a proximal end of the lead 100corresponding to the distal end 102 of FIG. 9. Here, each of the threetraces 110 terminate in a contact pad 108. Each contact pad 108 is thenelectrically connected with a connection terminal (as will be describedin a later section) which transmits stimulation energy from theimplanted IPG.

The thinness and flexibility of the dielectric film allow a variety ofdifferent types of leads 100 to be formed. Such types include layeredleads, circular leads, leads which curl or wrap around target tissue,leads which fold and expand, leads which surround a target tissue, leadsmounted on delivery devices and a variety of other leads designssuitable for stimulating specific types of target tissue, particularly aDRG.

FIGS. 11A-11B illustrate an embodiment of a layered lead 130. A layeredlead 130 comprises two or more individual leads which are layered andbonded together. FIG. 11A shows three individual leads 100 a, 100 b, 100c, each comprising a film structure 107 having an electrode 106 disposedthereon and a trace 110. It may be appreciated that each individual leadmay alternatively have a plurality of electrodes disposed thereon, suchas in an array. The three leads 100 a, 100 b, 100 c are staggered sothat the electrodes 106 are exposed and facing the same direction. Inthis embodiment, the traces 110 are positioned so that when the leadsare layered, the traces 110 are balanced across the layered lead 130.For example, the traces 110 may have opposing zig-zag or serpentineshapes when layered. This improves flexibility and handlingcharacteristics of the lead 130. FIG. 11B provides a side-view of thelayered lead 130 of FIG. 11A. Such layering allows each individual leadmore surface area, such as for redundant traces 110 for each electrode106. Since the leads are so thin, layering of the leads is still verythin and flexible. In addition, insulation layers may be bonded betweenone or more of the individual leads. In some embodiments, the proximalend of the layered lead is layered in a mirrored fashion so that each ofthe contact pads are exposed.

FIG. 12 illustrates an embodiment of a layered lead 130 in an expandedview. The three leads 100 a, 100 b, 100 c are staggered so that theelectrodes 106 are exposed and facing the same direction. In thisembodiment, the contact pads 108 are disposed on an opposite side ofeach of the leads 100 a, 100 b, 100 c. This provides for the contactpads 108 to also be exposed and facing the same direction when the leadsare layered.

FIG. 13 illustrates an example of a lead, such as lead 100 a, which maybe used in layering. The lead 100 a comprises an elongate film structure107 having a distal end 102 and a proximal end 104. FIG. 13A provides adetailed illustration of the distal end 102 of the lead 100 of FIG. 13.As shown, the lead 100 a includes at least one electrode 106 plated onthe “A-side” of the dielectric film structure 107. In this embodiment,one electrode is present FIG. 13B provides a detailed illustration ofthe proximal end 104 of the lead 100 a of FIG. 13. The proximal end 104includes a contact pad 108 on the “B-side” of the film structure 107which is used to connect with the IPG. In this embodiment, a circuittrace 110 extends from the electrode 106, along the “A-side” of thestructure 107, through a via to the “B-side” of the structure 107 andconnects with the contact pad 108. Thus, when a plurality of such leadsare layered, as in FIG. 12, stimulation energy may be transmitted fromeach of the staggered contact pads 108, through the associated traces,to the associated staggered electrodes 106 to stimulate the desiredtarget tissue.

FIG. 14 illustrates an example process and fixture for forming a layeredlead 130. Three individual leads 100 a, 100 b, 100 c are shown, eachcomprising a film structure 107 having an electrode 106 disposed thereonand a trace 110. In this embodiment, each lead 100 a, 100 b, 100 c is ofthe same length, however differing sized portions are shown for clarity.In addition, each lead 100 a, 100 b, 100 c has an alignment hole 132.The alignment holes 132 are used to assist in consistently and preciselyaligning the leads in a layered arrangement. A fixture 134 is shownhaving one or more posts 136 positioned thereon. The posts 136 are sizedand arranged so that the posts 136 are passable through the alignmentholes 132 when the leads 100 a, 100 b, 100 c are placed thereon. Oncethe leads 100 a, 100 b, 100 c are desirably positioned, the leads arebonded and fixed in this arrangement. The layered lead 130 may then beremoved from the fixture 134. In some embodiments, the resultingalignment holes 132 may be used for other purposes, such as for suturinga portion of the layered lead 130 to tissue during implantation.

It may be appreciated that the flexible circuit leads 100 may have avariety of shapes, sizes and dimensions. In particular, the distal end102 may be shaped to provide a particular electrode placement or toconform to a particular anatomy. For example, FIG. 15A illustrates alead 100 of the present invention having an oval, rounded or circulardistal end 102. Here, the film structure 107 is formed into the oval,rounded or circular shape and the electrodes 106 are arrangedtherearound, such as in a circular or arc pattern. This arrangement mayprovide a particularly desirable stimulation area or may more easilytarget a particular tissue, such as a dorsal root ganglion DRG which mayhave a circular or oval shape. FIG. 15B illustrates the lead 100 of FIG.15A positioned so that its distal end 102 is in proximity to a DRG. Asshown, the distal end 102 is positioned over the DRG so that itscircular shape substantially aligns with the circular shape of the DRG.The lead 100 is positioned so that the electrodes 106 face the DRG, andare therefore represented in dashed line. Appropriate electrodes maythen be selected for stimulation of the DRG based on desired painrelief. In some instances, the circular shape increases the number ofelectrodes 106 able to be used for stimulation and promotes selectivestimulation of the DRG.

In addition, the film structure 107 may be curled or rolled for ease ofdelivery and/or to wrap around a target tissue area. FIG. 16Aillustrates the distal end 102 rolled into a cylindrical shape. Such acylindrical shape may easily fit within a cylindrically shaped deliverycatheter or device. Thus, the lead 100 may be advanced from the deliverydevice in a rolled orientation wherein it may be deployed to an at leastpartially unrolled state. FIG. 16B illustrates the distal end 102partially unrolled and FIG. 16C illustrates the distal end 120 in anunrolled, flat orientation. In an at least partially unrolled state, thedistal end 102 may fully or partially wrap around a target tissue (suchas the DRG or including the DRG). In this configuration, the electrodesface each other having the target tissue therebetween. Appropriateelectrodes may then be selected for stimulation of the tissue areatherebetween based on patient interview for best relief of pain. In someembodiments, one or more obturators may be used to assist in unrollingand positioning of the circular lead 100.

FIG. 17 illustrates a lead 100 of the present invention having a prongeddistal end 102. Here, the film structure 107 is shaped to provide aplurality of elongate prongs 140, each prong 140 having an electrode 106positioned thereon. The prongs 140 may wrap around a delivery catheteror around a portion of the anatomy during implantation. For example,FIG. 18 illustrates the lead 100 of FIG. 17 positioned so that itsdistal end 102 is in proximity to a DRG. As shown, the distal end 102 ispositioned over the DRG and at least some of the prongs 140 wrap aroundthe DRG. The lead 100 is positioned so that the electrodes 106 face theDRG, and are therefore represented in dashed line. Appropriateelectrodes may then be selected for stimulation of the DRG based ondesired pain relief. In some instances, the pronged shape increases thenumber of electrodes 106 able to be used for stimulation and promotesselective stimulation of the DRG.

It may be appreciated that the film structure 107 is not only bendableand flexible, but also foldable and creasable. Thus, the leads 100 canform a variety of three-dimensional shapes which assist in wrappingaround particular tissues and anatomies. FIGS. 19-20 illustrate anembodiment of a shaped flexible circuit lead 500 of the presentinvention. The shaped lead 500 is comprised of two individual leads 100a, 100 b, each having at least one electrode 106 along one side of itsdistal end 102 and at least one corresponding contact pad 108 along theopposite side of its proximal end 104. Thus, the electrodes 106 and thecontact pads 108 reside on opposite sides of each individual lead 100 a,100 b. Lead 100 a is folded to form a crease 502 a along its lengthbetween the electrodes 106 and the contact pads 108 so that an acuteangle α is formed between the back of the distal end (opposite theelectrodes 106) and the face of the proximal end 104 having the contactpads 108 thereon. Likewise, lead 100 b is folded to form a crease 502 balong its length between the electrodes 106 and the contact pads 108 sothat an acute angle β is formed between the back of the distal end(opposite the electrodes 106) and the face of the proximal end 104having the contact pads 108 thereon. The angles α, β may be the same ordifferent. The leads 100 a, 100 b are assembled so that the creases 502a, 502 b are aligned and the angles α, β face away from each other, asshown. Consequently, the distal ends of the leads 100 a, 100 b form a Vshape wherein the electrodes 106 face each other within the mouth of theV. The leads 100 a, 100 b may optionally be bonded together to maintainthis shaped lead 500. Alternatively, the leads 100 a, 100 b may residein this arrangement, allowing the leads to slide in relation to eachother to adjust position.

FIG. 20 illustrates the shaped lead 500 wrapped around a target tissuearea, including a target DRG. As shown, the lead 500 is positioned sothe target tissue area resides between at least a portion of theelectrodes 106 along the mouth of the V. Thus, stimulation energy Eprovided by the electrodes 106, is provided to the tissue area layingtherebetween (within the V). This provides a higher likelihood ofstimulating the target DRG, since the exact location of the DRG withinthe target tissue area may not be known.

Positioning of the contact pads 108 on opposite sides of the assembledshaped lead 500 allows the joined proximal end 104 to easily beconnected to a connector (such as in a quick connect arrangement) whichis in turn connected with an IPG to supply the stimulation energy E.

It may be appreciated that other shapes may be formed, such as a “J”shape. Or, a triangular shaped lead may be formed having three distalend portions (forming a tripod shape). When deployed, this may coveringa larger target tissue area than the V or J shapes.

Likewise, the shapes may be formed by differing arrangements ofindividual leads or portions of leads. For example, the above described“V” shape may be formed by a longer flex circuit lead which is creasedand a smaller flex circuit bonded at the crease to form the constructwith an interconnect at the crease.

Delivery of the above described shaped lead 500 can be accomplished by avariety of methods. For example, the lead 500 may be delivered with theuse of a delivery device such as illustrated in FIGS. 21A-21B. In thisembodiment, the delivery device 520 comprises a flattened tube 522having a distal end 524 and a pair of obturators 526 a, 526 b which areadvanceable out of the distal end 524. The obturators 526 a, 526 b areeach comprised of a preformed spring metal or memory metal which is ableto curve or bend to form an angle (such as angle α or angle β) inrelation to the flattened tube 522.

FIG. 21A illustrates a first obturator 526 a extending from the distalend 524 of the tube 522. One of the individual flex circuit leads 100 ais attached to the obturator 526 a, such as with the use of a hook 528which holds the lead 100 a in place near the distal tip of the obturator526 a during deployment. The obturator 526 a bluntly dissects tissue asit is advanced, drawing the lead 100 a into the dissected tissue. FIG.21B illustrates a second obturator 526 b extending from the distal end524 of the tube 522. Another individual flex circuit lead 100 b isattached to the obturator 526 b, such as with the use of a hook 528.This obturator 526 b bluntly dissects tissue on the opposite side of thetarget so that the target lies near or within the “V” of the obturators526 a,526 b (and therefore between the electrodes 106 of the leads 100a, 100 b)

Once deployed, the leads 100 a, 100 b are released from the hooks 528and the obturators 526 a, 526 b are retracted into the tube 522, leavingthe leads 100 a, 100 b behind implanted in a “V” shaped configuration.Appropriate electrode pairs may then be selected for stimulation of thetissue area therebetween based on patient interview for best relief ofpain (in the case of DRG stimulation).

The flexible circuit leads 100 of the present invention are particularlysuitable for implantation in areas of the human body which benefit fromhighly thin and flexible leads. However, in some portions of theanatomy, delivery of such thin and flexible leads may be challenging dueto tortuous or constrained delivery paths. Therefore, the flexiblecircuit leads 100 may be attached to a delivery device, such as adelivery catheter 140, as illustrated in FIG. 22. The delivery catheter140 comprises an elongate shaft 142 having a lumen 144 therethrough forpassage of a stylet. Thus, the catheter 140 may be comprised of aflexible polymer material to retain the desirable flexibility of thelead 100 yet provide sufficient rigidity for deliverability. In someembodiments, the delivery catheter 140 remains in place with theflexible circuit lead thereattached wherein both remain implanted. Insuch embodiments, the flexible circuit lead 100 may wrap around thecatheter 140 so as to provide electrodes 106 on various surfaces of thecatheter 140. FIG. 23 illustrates a flexible circuit lead 100particularly suited for wrapping around a catheter 140. Here, theelectrodes 106 are aligned in a lateral row so that the electrodes 106will wrap around the circumference of the delivery catheter 140 whenmounted thereon. It may be appreciated that any of the flexible leads100 described herein may be mounted on or attached to a delivery device.

The leads of the present invention are typically passable through a 16gauge needle, 17 gauge needle, 18 gauge needle or a smaller needle. Insome embodiments, the electrode(s) of the present invention have a lessthan 3 mm square area, preferably less than 2 mm square area. In someembodiments, the electrodes have an approximately 0.6-1 mm square area.

Such reduced dimensions in electrode area and overall size (e.g. outerdiameter) are possible due to the increased specificity of thestimulation energy. By positioning at least one of the electrodes on,near or about the desired target tissue, such as the dorsal rootganglion, the stimulation energy is supplied directly to the targetanatomy (i.e. the DRG). Thus, a lower power may be used than with aleads which is positioned at a greater distance from the target anatomy.For example, the peak power output of the leads of the present inventionare typically in the range of approximately 20 μW-0.5 mW. Such reductionin power requirement for the leads of the present invention may in turneliminate the need to recharge the power source in the implanted pulsegenerator (IPG). Moreover, the proximity to the stimulation site alsoreduce the total amount of energy required to produce an actionpotential, thus decreasing the time-averaged power significantly andextending battery life.

As described previously, the proximal end 104 of each lead 100 isjoinable with an IPG to supply stimulation energy to the electrodes 106.FIGS. 24-25 illustrate an example proximal end 104 joined with aconnector 150 or portion of an IPG. As shown, the proximal end 104includes one or more contact pads 108 which are electrically connectableto the connector 150 via one or more pins 152. As shown in cross-sectionin FIG. 24, the connector 150 is able to make multiple connections withthe flexible circuit lead 100. The contact pads 108 are placed over pins152 that serve as both a means of locating the flexible circuit lead 100and making the connection with the conductive material of the contactpads 108. Once the proximal end 104 of the lead 100 is placed over thepins 152 a cover 154 is snapped into place, as shown in FIG. 25. The actof snapping the cover 154 on the pins 152 makes the electricalconnection between the contact pads 108 and the IPG and can connect manycontact pads 108 with just one connection action.

The connector cover 154 snaps in place with a predictable andsignificant force, enough to maintain the connection. The pins 152 arespring loaded to maintain the correct connection force. The springs maybe comprised of a flexible polymer, such as polyurethane or silicone, ora metal. The springs may be separate or built into the pins 152 thatmake the connection via MEMS or Wire EDM.

It may be appreciated that this connector 150 may be used for anymultiple lead connection that benefits from a simplified means forconnection. Such application may be for use with a medical device or anyelectronics connections.

Although the foregoing Invention has been described in some detail byway of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that various alternatives,modifications and equivalents may be used and the above descriptionshould not be taken as limiting in scope of the invention.

What is claimed is:
 1. A method for stimulating a tissue within a bodycomprising: positioning a lead comprising a flexible circuit having atleast one electrode so that at least one of the at least one electrodeis disposed near a dorsal root; and supplying electrical energy to theat least one of the at least one electrode so as to stimulate at least aportion of the dorsal root.
 2. A method of claim 1, wherein the portionof the dorsal root comprises a dorsal root ganglion.
 3. A method ofclaim 1, further comprising advancing the lead through a foremen.
 4. Amethod of claim 1, further comprising advancing the lead through anepidural space.
 5. A method of claim 1, further comprising joining thelead with an implantable pulse generator.
 6. A method of claim 5,further comprising implanting the lead and the implantable pulsegenerator wholly within the body.
 7. A flexible circuit lead forstimulating a body tissue comprising: an elongate structure having adistal end configured to be positioned near a dorsal root and a proximalend coupleable with a pulse generator, wherein the structure comprises adielectric film; at least one electrode disposed near the distal end;and at least one conductive trace extending from the at least oneelectrode toward the proximal end so that stimulation energy istransmittable from the coupled pulse generator to the at least oneelectrode so as to stimulate the at least a portion of the dorsal root.8. A flexible circuit lead as in claim 7, wherein the at least oneelectrode is comprised of a biocompatible conductive metal, alloy orcombination of these plated onto the dielectric film.
 9. A flexiblecircuit lead as in claim 8, wherein the biocompatible conductive metal,alloy or combination includes gold, titanium, tungsten, titaniumtungsten, titanium nitride, platinum, iridium or platinum-iridium alloy.10. A flexible circuit lead as in claim 7, wherein the dielectric filmhas a thickness in the range of approximately 7.5 to 125 μm.
 11. Aflexible circuit lead as in claim 7, wherein the at least one electrodecomprises a plurality of electrodes arranged substantially linearlyalong a longitudinal axis of the distal end.
 12. A flexible circuit leadas in claim 7, wherein the at least one electrode comprises a pluralityof electrodes arranged substantially linearly along a horizontal axis ofthe distal end.
 13. A flexible circuit lead as in claim 7, wherein theat least one electrode comprises a plurality of electrodes arranged in asubstantially circular or arc shape.
 14. A flexible circuit lead as inclaim 7, wherein the distal end has a pronged shape including at leasttwo prongs.
 15. A flexible circuit lead as in claim 8, wherein one ofthe at least one electrodes is disposed near a tip of one of the atleast two prongs.
 16. A flexible circuit lead as in claim 7, wherein thedistal end is configured to wrap around the body tissue.
 17. A flexiblecircuit lead as in claim 7, wherein the distal end of the elongatestructure is passable through a needle.
 18. A lead for stimulating abody tissue comprising: an elongate structure having a proximal endcoupleable with a pulse generator and a distal end having two edgeswhich are capable of being positioned in opposition, wherein the distalend includes at least two electrodes which generally oppose each otherwhen the edges are positioned in opposition so as to stimulate the bodytissue.
 19. A lead as in claim 18, wherein the distal end forms aV-shape or U-shape when the two edges are positioned in opposition whichallows the body tissue to be positioned at least partially within theV-shape or U-shape.